pub fn new_birthday_probability(n: u32) -> f64 {
    if n < 2 { return 0.0f64; }
    let mut probability_unique = 1.0;
    for i in 0..n {
        probability_unique *= (365 - i) as f64 / 365.0;
    }
    
    1.0 - probability_unique
}
